As the thermal transfer sheet utilized in the electrical transfer process where heat is generated by applying an electric current from an electrode head and the transfer is effected by this heat, there has been adopted a structure in which a resistor layer generating heat by an electric current supplied from an electrode head is formed on one surface of a substrate sheet and a dye layer containing a dye that can migrate under heating and can be transferred to a receipt sheet, such as a sublimable dye, is formed on the other surface of the substrate sheet, and a structure in which electroconductive fine particles are incorporated into a substrate sheet to cause the substrate sheet per se to act also as a resistor layer and a layer of a dye as mentioned above is formed on one surface of the sheet.
Most of resistance values of these resistor layers have, in general, a negative temperature coefficient or a temperature coefficient of zero, and even if the resistance values have a positive temperature coefficient, the value of the positive temperature coefficient is small. Accordingly, at the time of generation of heat by application of an electric current, with elevation of the temperature, the resistance value is reduced and super heating is caused by flowing of an increased electric current, or even if the resistance value is not reduced, an effect of controlling an excessive elevation of the temperature is insufficient. Therefore, problem such as fusion sintering of the thermal transfer sheet or breaking of the thermal transfer sheet are often occur.
Furthermore, in case of a thermal transfer sheet of this type, if long-run transfer is carried out, the electrode head is often deteriorated by the friction between the electrode head and the resistor layer. Moreover, a higher transfer energy is required for the thermal transfer sheet of the sublimation type than for a thermal transfer sheet of the fusion type, and therefore, the temperature of the resistor layer by generation of heat becomes much higher, with the result that heat fusion bonding is caused between the electrode head and the resistor layer, and insufficient transfer or insufficient running often occurs.